Abstract

Irreversible absorption of light in any material requires that the coherence of the initial photoexcited state be lost. In quantum-engineered semiconductor systems, decoherence cannot be treated merely phenomenologically, and coherent phenomena play a dramatic role, even in the linear optical properties,¹ We have devised an ultrafast coherent spectroscopy that directly tracks the evolution of the electron-hole phase after excitation with a 100-fs laser pulse. In high-quality quantum well samples, this general technique uncovers a coherent response differing strongly from that observed on incoherent excitation.

© 1996 Optical Society of America